[JDSTX38]

Because air cooled engines run hotter the hotter the ambient temperature gets 10W30 is not recommended In my owners manual if you mow in summer temperatures in the upper 80s and above.

Is 30W oil the best oil to use for air cooled engines for non winter use? According to the chart it has hottest temperature range.

According to the owners manual for STX38 oil temperature limits
5W30 -31 +50F ambiant temp
10W30 -4 +86F
10W40 -4 +104F
30W 32 +122F

 

[Sispro]

Yes use 30W only the other oil is to thin

 

[slomo]

I agree with both you guys. When in doubt over 50F use 30w oil.

Think the reason people use 5w-30 or insert any other non 30w oil for over 50F temps is that's all they have on hand in the garage. Also cheaper to buy the lighter oils compared to 30w. And lets face it, American's are lazy. Then we troll Craig's List and find all kind of blown up mowers for cheap. Wondering what happened to them?? Most push mowers hold 18 to 20 OUNCES of oil. Freak'in people are too lazy to change it. I appreciate it though so I can score cheap mowers.

slomo

 

[SwedishRider]

Is 30W oil the best oil to use for air cooled engines for non winter use?

No. Briggs & Stratton recommends full synthetic 5W-30 as the best possible protection in all seasons (at least for their engines).

From Briggs & Stratton's website: http://www.briggsandstratton.com/us/en/support/faqs/engine-oil-recommendations

Personally, I use Amsoil ASE 10W-30/SAE 30 in my small air-cooled engines: http://www.amsoil.com/shop/by-produ...10w-30-sae-30-small-engine-oil/?code=ASEQT-EA

 

[honda4514]

:ditto::ditto::ditto: The only thing that goes in my mowers all year round is Amsoil 10w30 synthetic. Been using it since it came out with no problems.

 

[mowerbeast]

I've always used SAE30 and never had an issue (knock on wood). The only exception to that is in the winter when I was using my lt4000 for snow plowing, then I was using 10w-30. All the manuals for my machines say use SAE30 and that's what I use. All my stuff is over 10 years old though, newer machines might be different. My recommendation is do what the manual says.

 

[TUDOR]

Those temperatures are for a reasonable starting load and flow rate for the bearings at ambient temperature. Once the engine has run for a while doing work, the oil temperature will be in the upper range of the 100 - 200° scale, no matter what the grade of oil or the ambient temperature. It just takes a while longer to get there in the colder temperatures.

The 5W or 10W means that the modifyers used in the additive package will allow it to flow at the correct rate for bearings at the colder temperatures, and the -30 means that it will flow at the correct rate when the engine is warmed up to operating temperature. You can use a lighter weight oil at higher ambient temperatures without worry, but heavy weight oil at colder temperatures weighs heavily on the starter motor and battery and runs a risk of poorly lubed bearings and the wear associated with that situation.

My tractor can see temperatures from -30° F to +80° F in a 3 month time frame from March to May, and again from October to December. I try to schedule the oil changes in mild weather in September or October for the heavy use in winter. Multi grade oil is the only option.

 

[suspicionofignorance]

IMO...Most of what TUDAR mentions about the multigrade oil is correct...but it's been my understanding that the actual oil is what ever the 'low" range number is...10w -30 is therefore 10 weight base oil...the additive /modifyers are simply for the high temp range...where they swell up and prevent the unwanted thinning out...5w is 5 weight and very thin oil...I would have concerns about using it in older engines with wider bearing clearences..and in hot summers....Did see a older Briggs chart that showed 10w-30 only useable to 85 deg F...then saw same chart , few yrs later showing it up to 100 deg..Depending on where you live...think st 30w is best for older engines..at temps above 40 deg...or 10w-30 for any OHV eng...Just my opinon..

 

[SonnyT]

Base is 10 for 10w30. Base is 5 for 5w30 etc. Low number is the base grade and then additives make it go to the higher number when hot.:fing32:

 

[suspicionofignorance]

Yup....Thats exactly what I was saying....5W-30 is really a 5 weight base oil...no modifyers help the extreme thin viscosity of it at warm ambient temps...So why is it becoming more and more recommended for air cooled mowers in hot summer use.,...?
Is 0w-30 going to be recommend soon also..? If so, maybe the oil companies are looking to reduce manufacturing costs...cuz NO auto eng is using straight weight oils..and auto/truck is prob 99% of their sales..and theyre 'biased" for miles/gal..EPA,..

 

[TUDOR]

Why do cars and trucks use multi-grade oils? Because of wide variations in ambient temperatures between oil changes.

While some owners have high mileage numbers in relatively short time frames, others have low mileage in much longer time frames. The population in general is getting older and not driving back and forth to work as much. An oil change done at the proper time intervals (well short of the normal mileage interrvals) may have to deal with winter temperatures if done in February and warm spring temperatures in May. That can easily span from - 30° to +80° F in the northern states and Canada.

GT's deal with the same circumstances. Many do less than 50 hours of service in 12 months between mowing and snow removal.

 

[JohnDeere318Guy]

My Onan air-cooled engines love to burn 10w30 if I run that oil in the summer, my Kawasaki liquid cooled FD620D in my scag ran fine on 10w30 in the high heat of summer.

 

[Walt 2002]

Strange to me that B&S would recommend 5W-30 synth when all the sites and Service Manuals for specific engines recommend SAE 30 for above 50 degrees or so with 5W - 30 synth not recommended in the upper ranges.

Walt Conner

 

[suspicionofignorance]

Its a conspiricy...Ha!...Why is 5w synth ok at full swings of temp...but convential 5w is not ? Assuming they both are 5w base oil in the multi vis...Why did the national chain, Jiffy Lube stop dispensing 10w-30,,all overhead dispensers are now 5w-30...?Its all for the money...EPA mileage MPG mandates for cars/trucks...I think it's cheaper for the manufactures to risk some degree of warranty failures..than to pay the fine to the FEDS..as I'm sure their accountants have told them.
Our Small engine world...minor concern..and Chinese made engines are low cost..[throw aways]....Nobody cares if you get 5yrs or 15 yrs life out of the engines..Residental...and from neighbors that I see...they don't care either...run it -stops, buy another new one.

 

[coach]

I've been running 10w-30 synthetic in my stx38 for 22 years with no ill effects.
Now if there was a way to keep things from falling off or the hood from cracking, I'd be happy.

 

[suspicionofignorance]

That's what we need to hear...actual long term owners opinons..such as Coach..His use was synthetic multigrade...there does seem to be a difference in it compared to conventional at the low ends...Not sure why..as they both are very thin 10w...offering very little cushioning for the bearings in hot summers..Then again, Maryland does Not get as hot as many southern states during the long summers...A lot has to do with where we live..and whether we're dealing with older "flathead" engines or OHV and OHC..the way I see it.

 

[coach]

One thing I've heard/read is synthetic oil runs 20 -50 degrees cooler because of reduced friction and better heat dissipation. While Md. May not get as hot or for as long as the Deep South , I've done plenty of cutting in 90 degree plus weather. Although this year has been especially mild with not a lot of days out of the 80's.
Ps. If I could find a straight 30 weight in a synthetic I might use it. I've yet to see it on a store shelf.

 

[suspicionofignorance]

Good info , Coach...Yes to the st 30 weight in synthetic...I had another thread on that very same thought...Why 'won't' any major oil company make syn in straight weight....?
Dunno..!
My only concern is 'long term' ware on the sleeve bearings in older engines..from reduced cushioning of 10w [or now 5w----or OMG, 0w]...All in all, we owners may not keep the engines long enuf to evaluate long term problems..And besides, if your engine suddenly"threw a Rod'...would you be able to "directly' correllate to the type of oil ?

 

[slomo]

Why do cars and trucks use multi-grade oils? Because of wide variations in ambient temperatures between oil changes.

While some owners have high mileage numbers in relatively short time frames, others have low mileage in much longer time frames. The population in general is getting older and not driving back and forth to work as much. An oil change done at the proper time intervals (well short of the normal mileage interrvals) may have to deal with winter temperatures if done in February and warm spring temperatures in May. That can easily span from - 30° to +80° F in the northern states and Canada.

GT's deal with the same circumstances. Many do less than 50 hours of service in 12 months between mowing and snow removal.

Cars and trucks are water cooled engines. They can run multi vis oils. Air cooled engines will shear down a 5w what ever in no time. Air cooled engines run much hotter than water cooled engines do. Stick with 30w in air cooled mowers, unless your manual states other info. Over 50F run a 30W.

slomo

 

[TUDOR]

Cars and trucks are water cooled engines. They can run multi vis oils. Air cooled engines will shear down a 5w what ever in no time. Air cooled engines run much hotter than water cooled engines do. Stick with 30w in air cooled mowers, unless your manual states other info. Over 50F run a 30W.

slomo

Define 'no time'.

Recommended oil change intervals for air cooled small engines are less than half of the recommended intervals for cars and trucks. A typical car running errands around town will get up to 150 hours put on the engine with a 3000 mile oil change interval. The recommended interval for air cooled small engines is 25 - 50 hours, depending on when it was made and who made it.

If small engines operated as hot as you infer, most would seize the main bearings in short order. The bottom end of an automotive liquid cooled engine is not cooled except by lubrication, the same as air cooled engines.

Most aircraft piston engines are air cooled and use multi grade motor oil. They can see temperatures of 80+° on take off, -20° during the flight, and 30° or less on landing at their destination only a short time later.